Method and apparatus for cutting cores



March 5, 1957 UHLAND 2,783,969

METHOD AND APPARATUS FOR CUTTING CORES Filed April 14, 1953 IN VEN TOR. fimwm,

ATTORNEY.

METHOD AND APPARATUS FOR CUTTING CORES Homer E. Uhland, Lakeland, Fla, assignor to International Minerals & Chemical Corporation, a corporation of New York Application April 14, 1953, Serial No. 348,727

6 Claims. (Cl. 25-13) This invention relates to drilling equipment. More particularly it relates to apparatus for recovery of core samples drilled out of the formation at the bottom of prospecting wells or holes. Still more particularly it relates to the construction of core barrels for rotary drilling.

in the past various arrangements have been devised for receiving cores cut from the formation at the bottom of holes and for removing such cores to the surface of the ground so that data regarding the nature of the formation may be obtained. In core drilling, the limiting point in core recovery is reached when the sum of the weight of the core and the wall friction of the core counterbalances the pressure created by the downward movement of the barrel. in order to obtain longer cores, it is necessary to reduce either or both of the counterbalancing factors.

in one embodiment of core taking apparatus described by Harrington in Patent No. 2,147,896, a core barrel is described having a closed head and having two ball valves in the head of the core barrel which two valves are superimposed upon one another in the one fiuid fiow channel. The bottom ball is seated by gravity and the upper ball is seated against an overhead valve seat. In order to release fluid from the core taker and to accept the drill core into the core barrel, a weight must be dropped down the drilling stem to actuate a plunger and thus hold the upper valve open so long as the weight is at the bottom of the drill stem.

Such an apparatus has many disadvantages. No fluid travels through the core barrel to keep it clear of debris during the time it is being lowered into the well or hole. in addition the plunger is easily jammed or fouled, and in order to put it back into operation the entire drill stem must be pulled. Further, after the drill stem and core barrel has been lowered into the hole, no sample can be taken until the drill stem rods have been disconnected and the actuating ball dropped down the drill stem and the rods reconnected, all of which operations are time consuming.

it is an object, therefore, of this invention to overcome the shortcomings and disadvantages of apparatus heretofore in use. It is another object of this invention to provide a sample receiving core barrel for rotary drilling which may be lowered into the well and at the same time have fluid forced therethrough to Wash away cuttings and other debris which would normally accumulate in a closed head core barrel.

It is a further object of the invention to provide a method of operation which will permit the coring of larger samples.

It is a further object of the invention to provide apparatus which can be switched from operation under positive fluid pressure to operation under vacuum while the core barrel is at the bottom of the drill hole.

It is still another object to provide a device which when it is seated in the bottom of a hole is ready for operation nited States Patent 2,783,969 Fatented Mar. 5, 1957 "ice without having to disconnect drill stem to render the device operative.

it is still another object to provide a device of the character set forth in which the upper end of the core barrel will have a pressure responsive element adapted to admit fluid to the core barrel and separate release means to permit upward flow of fluid from the core barrel during the taking of a core.

These and other objects of the invention will be apparent to those skilled in the art from the following description. During the drilling stem which is usually hollow pipe sections has water or drilling mud forced down through the stem and through the cutting bit. This fluid flows back to the top of the hole so that the cuttings are carried away from the drill bit. When cutting a core sample, the core barrel replaces the cutting or drill bit.

The method of obtaining core samples, according to the instant invention, comprises maintaining a flow of fluid through the core receiver until the receiver is in secure contact with the formation to be cored, changing the pressure conditions within the core receiver from superatmospheric pressure to subatmospheric pressure, actuating the core receiver to cut a core, and maintaining subatmosp-heric pressure on the core until the receiver is removed from the hole.

In the operation, superatmospheric pressure is maintained by pumping a fluid such as water or drilling mud down the drill stem under a pressure generally in the range of between about pounds per square inch and about 200 pounds per square inch, although higher pressure may be used. This fluid pressure overcomes the resistance of the fluid control means such as a spring loaded upwardly biased valve opening the flow course and permitting the fluid to flow through the receiver or core barrel keeping is clear of loose particles or debris. When the receiver is securely seated on the formation in the bottom of the hole, the fluid pumping is stopped, and by means of valving vacuum is drawn on the receiver directly or through the drill stem, preferably the latter. This vacuum or reduced pressure is generally of the order of about 5 inches to about 15 inches of mercury, although higher and lower pressures may be used, and is maintained during the core cutting and removal of the core from the hole.

I-f operation is carried out Without the aid of vacuum, when the core barrel is seated in the bottom of the drill hole, it will have been freed of debris by reason of the passage through the barrel of fluid under positive pressure. After the core barrel is seated, the pumping of fluid ceases and core cutting may be immediately started. The drill stem is then rotated and/or hydraulically pressed and during the cutting, the core barrel settles over the core section, liquid in the barrel being forced out through the separate gravity seated ball valve also in the head of the core barrel. When the core barrel is full, the barrel is removed from the hole by pulling out the drill stem, and suction developed in the core barrel due to the fact that both fluid control means are in closed position retains the sample therein during the removal operation.

The core barrel apparatus of this invention 'will be more fully understood from the following description and by reference to the drawings in which Figure 1 is a vertical view partly in cross section of the core barrel mounted for use.

Figure 2 is a vertical cross sectional view of the core barrel head.

Figure 3 is a plan View of the core barrel head.

Referring more particularly to the drawings, the numeral 10 indicates the .core barrel head secured by a suitable connecting means 11 as by a threaded joint to a reducing coupling or adapter 12. Adapter 12 is shown disengageably connected to drill stem 13 which is internally threaded as at 14 to receive said adapter.

Core barrel head is internally threaded at its lower endas at 15 to receive a core barrel 16, which in turn is adapted at its lower end with cutting teeth 17 either integrally formed or mounted thereto as by means of a drilling shoe.

Core barrel head 10 is provided with a transverse partition or wall member 18 adapted with bores 19 and 2t) connecting the chamber 21 of the adapter 12 with the chamber 22 formed below wall member 18. Wall mem ber 18 may be integrally formed With core barrel head 10 or secured therein in water tight engagement as by welding or other suitable means.

Bore 19 is countersunk at 23 to form a valve seat for suitable fluid flow control means 24 as, for example, a gravity seated ball. Secured to wall member 18 as by tack welding, brazing, or the like is an annular member 25 of a diameter sufficient to permit free vertical action of the ball 24 and having circumferentially spaced apertures 26 therein. Annular member 25 has its longitudinal axis in alignment with bore 19. Escape of ball 24 from the annular member or ball race is prevented by a suitable blocking piece 27, such as a bar secured against movement by a suitable latching unit.

Bore is countersunk on the under side of wall member 18, as at 28, to form a seat having a 45 degree chamfer for a fluid flow control or valve member 29 such as a ball. Valve member 29 is biased into contact with valve seat 28 by suitable adjustable pressure means 30 such as a spring. Spring 30 is mounted with its axis in axial alignment with the axis of bore 20 and is held in place by suitable securing means 31, here illustrated by four support members 32 such as machine screws or adjustable studs. Studs 32 are so spaced as to form lateral support for spring 30, and have secured thereto by suitable means a plate 33 designed to prevent longitudinal movement of the spring and to exert suitable compressing pressure thereon.

When prospecting with the apparatus above described, the core barrel is secured to the drill stem and lowered into the drill hole. Fluid is then pumped through the drill stem as in the normal drilling operation to positively wash out the drill hole and keep the core barrel free of debris. The spring loaded valve 29 is generally designed to open when the fluid pressure in the drill stem exceeds approximately 150 pounds per square inch. When the core barrel is seated on the bottom of the hole, pumping-is stopped and thespring loaded valve closes. Coring then can proceed immediately by the rotation of the drill stern and the attached core barrel. As the core rises in the barrel, air and fluid trapped between the core and the core barrel head escape through the gravity seated release valve. Upon completion of coring, the core barrel and drill stem is withdrawn from the hole. Tests over a period of time comparing the core barrel of this invention with a core barrel of a design similar to that shown by Harrington which must be rendered operative by dropping a valve down the drill stem have shown that the average footing cored per hour in the case of the core barrel of this invention increased an average of about 50%.

Having thus fully described and illustrated the character of my invention, what is desired to be secured and claimed by Letters Patent is:

l. The method of obtaining core samples which comprises lowering into a bore hole a core receiver attached to a drill stern, maintaining a flow of predominantly liquid medium through the receiver until the receiver is incontact with the formation to be cored to keep debris which might be present in the bore hole out of the bottom of said receiver, arresting liquid medium flow while liquid medium remains in the receiver, actuating the core receiver to cut a core to cause flow from said receiver of liquid medium therein into the drill stem, and applying a vacuum on the receiver between the top of the receiver and the core to create a pressure differential between the pressure in the interior and the pressure of the liquid medium exterior of the receiver in the bore hole to retain the core in the receiver until the receiver is removed from the hole.

2. The method of obtaining core samples from a bore hole which comprises pumping predominantly liquid medium under a pressure between about pounds per square inch and about 200 pounds per square inch through a core receiver attached to a drill stem until the receiver is in contact with the formation to be cored to keep debris which might be present in the bore hole out of the bottom of said receiver, stopping the pumping of liquid medium while liquid medium remains in the receiver, drawing a vacuum of between about 5 inches and about 15 inches of mercury within the receiver to create a differential pressure between the pressure in the interior and the pressure of the liquid medium exterior of the receiver in the bore hole, actuating the receiver to cut a core and thereby cause flow from said receiver into the drill stem of liquid medium therein, and maintaining the vacuum directly on the core until the receiver is removed from the hole.

3. In a sample taking device, a head member, a core taking barrel depending therefrom, means at the upper end of said head member by which it may be connected to a drill stem for lowering it and for rotating it within the drill hole, a transverse partition member in said head member defining with said barrel a core receiving chamber, fluid passage means in said transverse partition member placing said chamber in communication with the drill stem, valve means carried by said transverse partition member for controlling flow of fluid through said fluid passage means, said valve means including means tending to prevent flow of fluid into said chamber from the drill stem while permitting such fluid flow in response to fluid pressure within the drill stem which is a predetermined amount greater than the pressure in said chamber, said valve means also including means preventing fluid flow into said chamber while permitting flow of fluid from said chamber into the drill stem when the chamber pressure exceeds the pressure in the drill stem.

4. In a sample taking device, a core taking barrel, a head member releasably attached to said barrel, means at the upper end of said head member by which it may be connected to a drill stem for lowering it and for rotating it within the drill hole, a transverse wall member in said head member defining with said barrel a core receiving chamber, two spaced ports in said transverse partition member placing said chamber in communication with the drill stem, valve means mounted in conjunction with one of said ports preventing flow from said chamber into the drill stem and biased for closing said port against fluid inflow from the drill stem, and a check valve mounted in conjunction with the other of said ports whereby fluid in the core receiving chamber may be discharged into the drill stem.

5. In a sample taking device, a head member, a core taking barrel depending therefrom, means at the upper end of said'head member by which it may be connected to a drill stem for lowering it and for rotating it within the drill hole, a transverse partition member in said head member defining with said barrel a core receiving chamber, two spaced ports in said transverse partition member placing said chamber in communication with the drill stem, a spring valve mounted in conjunction with one of said ports responsive to fluid pressure in said drill stem to admit fluid from said drill stem into said chamber, and a gravity seated ball valve member mounted in conjunction with said other port to control fluid flow from the core receiving chamber into the drill stem.

6. In a sample taking device, a head member, a core taking barrel depending therefrom, means at the upper end of said head member by which it may be connected to a drill stem for lowering it and for rotating it within the drill hole, a transverse partition member in said head member defining with said barrel a core receiving cham- 5 her, two spaced ports in said transverse partition member placing said chamber in communication with the drill stem, a spring valve mounted in conjunction with one of said ports to open under drill stem fluid pressure in excess of about 150 pounds to admit fluid from said drill stem into said chamber, and a gravity seated ball valve member mounted in conjunction with said other port to control fluid flow from the core receiving chamber into the drill stem.

References Cited in the file of this patent UNITED STATES PATENTS Hohmann et a1 Mar. 9, 1937 Harrington Feb. 21, 1939 Edwards Sept. 10, 1940 Knight et al Dec. 29, 1953 

